Sigh. Estimation and mental math techniques are good in some situations, but rarely in isolation. These folks are misguided; this line of thinking was can result in stupid errors like the Mars spacecraft that failed due to a unit error (centimeters and inches are not equivalent units).
As for the "Mathematics for Human Survival"...it's a lame and pathetic excuse for a college textbook. The fact that the book is even being recommended for use in teaching such concepts as percentages in a college-level class is a sad reflection of the dumbing down of the U.S. education system. I learned and mastered both concepts in elementary school, but then again, that was in the early 1990s.
Propaganda doesn't get us anywhere. Neither does statistical manipulation or dumbed down mathematics.
Our ignorance of "the same mathematics that we did years and years ago" will, however, reduce America's competitive advantage, relative to such rising powers as India and China.
“Propaganda doesn’t get us anywhere.”
It gets the anti-US left everywhere they want to go - destroying America’s superiority.